Food chillers, such as the auger type poultry chillers, are used in poultry processing plants for reducing the temperature of the birds after the birds have come off the processing line and have been defeathered, eviscerated and otherwise have been made oven-ready, for packaging and shipment to the consumers.
A typical auger type poultry chiller includes an elongated, half-cylindrical tank having a rotary auger placed therein. Water is placed in the tank and is recirculated through a cooling system such as a refrigeration system, with the water directed to a first end of the tank and reclaimed at a second end of the tank. Birds are placed in the tank at its second end and the birds are advanced by rotation of the auger toward the first end. The auger typically rotates at one revolution for every three to five minutes. This arrangement moves the water in a counter flow relationship with respect to the movement of the birds, so that the birds are contacted by the coldest water at the delivery end of the tank.
This type of poultry chiller is generally known in the prior art, as exemplified by U.S. Pat. Nos. 5,868,000 and 6,308,529.
One of the phenomena of the prior art poultry chillers is that the birds tend to migrate from one lateral side of the auger shaft (the “dead” side of the tank) to the other lateral side of the auger shaft (the “pulling” side of the tank) as the birds advance along the length of the tank. The conditions that cause the phenomena is that as the water in the tank moves along the length of the tank a large percentage of the water flows about the perimeter of the auger blades, between the blades and the side of the tank. The birds in the water tend to follow the water toward the perimeter of the auger blades and into contact with the auger blades. When the birds contact the auger blades the rotary motion of the auger blades urges the birds from the dead side to the pulling side of the tank. The auger blades move in an arcuate path first downwardly into the water through the dead side of the tank, then beneath the auger shaft, and then upwardly on the pulling side of the auger shaft and then out of the water in the tank. The birds tend to follow this movement to the pulling side of the tank until the blades reach the surface of the water at the pulling side of the tank. Then the buoyancy of the birds and the movement of the water between the perimeter of the auger blades and the side of the tank tend to hold the birds there. This usually results in most of the birds at each auger flight forming a mass or “clump” of birds on the pulling side of the tank, at the side wall of the tank, at the surface of the water.
This accumulation of birds in a relatively dense mass on the crowded pulling side of the auger shaft tends to reduce the chilling effect of the water against the birds. The birds in the mass are so densely packed next to one another compared to the surrounding water that the chilling capacity of the water about the mass of birds is substantially reduced.
Another effect of the massing of the birds as described above is that there is less circulation of the water among the birds. It is well known that the rapid circulation of chilled water about the birds results in a more rapid removal of heat from the birds.
The water level in the prior art chiller tanks usually is maintained at or only slightly higher than the height of the shaft of the auger. The shaft functions as a dam to prevent the birds in the mass of birds on the pulling side of the tank from moving across the shaft into the space behind the auger.
In order to increase the load capacity of a poultry chiller, additional water can be added to the tank. FIG. 1 of the drawings shows a prior art poultry chiller that is filled with water to a level above the auger shaft. The chiller tank 10 is a one-half cylinder tank that has a lower portion 12 in the form of a one-half cylinder and vertical wall extensions 14 and 15. The water level is shown at 21. The helical auger blade 16 in the tank is rotated on its auger shaft 18 in the direction as indicated by arrow 20, inducing the birds 22 to move laterally from the dead side 24, beneath the auger shaft 18, to the pulling side 25 of the chiller tank 10. In this example the water level 21 is higher than the shaft 18. When the birds move to a level in the water adjacent the side wall of the tank that is higher than the auger shaft 18, those birds adjacent the side wall of the tank eventually reach an approximately triangular shaped gap 26 where the vertical extension 15 of the one-half cylinder tank 12 diverges from the circular perimeter of the helical auger blade 16. The water moving through the gap induces any birds that are suspended near the water level 21 and adjacent the vertical wall extension to move from the pulling flight to the following flight of the auger. This results in some of the birds falling behind by one auger segment and spending a longer time than necessary in the tank.
As shown in FIGS. 2 and 3, a solution to the loss of birds from one auger flight to the following auger flight in a high water situation through a triangular shaped gap, such as the gap 26 of FIG. 1, was to eliminate the triangular gap. This was accomplished by making the one-half cylinder chiller tank more nearly cylindrical, as shown by the tank 32. The vertical wall extensions of FIG. 1 were wrapped about the auger. But if high water is used in the chiller tank of FIG. 2 as shown by water level 31, there is a hazard that some of the birds 22 that accumulate on the pulling side of the tank will float over the auger shaft 28. If birds should inadvertently cross over the auger shaft 28 by the over-filling of the tank with water and by the accumulation of too many birds on the pulling side of the tank, the birds crossing the shaft will fall behind in the next flight of the auger. This is illustrated in FIG. 3 where the solid lines of the auger 33 illustrate the upper portions of auger positioned above the water level and the dashed lines of the auger 33 illustrate the lower portions of the auger positioned below the water level. The birds 22A, 22B, and 22C have moved away from their mass of birds 23 and crossed over the auger shaft 28. Once the bird shown at 22A crosses the auger shaft it enters the dead side of the tank, and the contact of the downwardly moving surface of the auger against the bird on the dead side of the tank tends to move the bird from position 22A toward 22B and eventually under the auger shaft 28 to position 22C. This results in the birds falling behind to the next accumulation of birds and the birds remain in the chiller an additional 3 to 5 minutes, which is longer than the time required for chilling the bird. It also places extra birds in the following auger flight so that the chilling efficiency of the following auger flight tends to be reduced.
Another problem in the birds falling behind to a following auger flight in a prior art bird chiller is created when the entire poultry processing line is progressively shut down for a work break. The delivery of birds to the chiller is interrupted for a certain time interval, such as 18 minutes, so the birds previously delivered to the chiller can move on through the chiller but the absence of incoming birds creates a gap in the line of birds to be processed by the following work stations. When the last birds are removed from the tank the following process stations have no birds to process and the workers at the following work stations have the opportunity to take a work break.
However, if the birds in the chiller have fallen behind to the next auger segment, the birds will continue to be delivered from the chiller to the following work stations for a longer time, so that the workers down stream from the chiller do not have as much time on their work break. Even if the operation of the chiller is not interrupted for a work break, the non-uniform delivery of birds from the chiller reduces the efficiency of the following processing line.
It is to the above noted problems that this invention is directed.